1. Technical Field
The present invention relates generally to a pulse injection apparatus and, more particularly, to a coupling clamp-type pulse injection apparatus, which is used for a test in the analysis of the effects of a conductive high-power electromagnetic pulse (EMP).
2. Description of the Related Art
High-power electromagnetic pulses may be divided into nuclear electromagnetic pulses and non-nuclear electromagnetic pulses. A nuclear electromagnetic pulse typically denotes a high altitude electromagnetic pulse (HEMP) caused by nuclear explosion occurring at an altitude of 30 km or more. A non-nuclear electromagnetic pulse denotes intentional high-power electromagnetics (HPEM) caused by instantaneous discharge or microwave resonance, an electromagnetic pulse caused by the grounding of a lightning bolt (lightning electromagnetic pulse: LEMP), a geomagnetic storm caused by sunspot activity of the sun, etc.
In order to defend a device against a high-power electromagnetic pulse, the test source of high-power electromagnetic pulse generation equipment, a measurement tool for analyzing effects on a device under test such as an electronic device, etc. are required.
Tests for analyzing the effects of such a high-power electromagnetic pulse may be chiefly divided into a radiative type and a conductive type. A radiative effect analysis test is configured to analyze which effect has been exerted on a device under test by radiating a high-power electromagnetic pulse to the air using pulse generation equipment and an antenna. A conductive effect analysis test is configured to analyze which effect has been exerted on a device under test by transferring overvoltage and overcurrent, also known as surge, occurring when a high-power electromagnetic pulse is induced in a power cable or a communication cable, to be the device under test.
In the case of two types of tests, a high-power electromagnetic pulse may be directly coupled to a cable such as a power cable or a communication cable. However, the radiative test is characterized in that the configuration of a test environment is complicated and thus cost is high, and in that the influence of a distance and a surrounding environment is large, and thus a pulse having intensity lower than the output of pulse generation equipment is coupled to the cable. Compared to this, the conductive test is configured such that a pulse is directly injected into the cable, and is advantageous in that the configuration of a test environment is simpler than that of the radiative test and a higher cable coupling voltage may be obtained.
For such a conductive effect analysis test for a high-power electromagnetic pulse, there is essentially required an injection device capable of coupling a high-power electromagnetic pulse to a cable.
In the case of a nuclear electromagnetic pulse (HEMP), the rising time of an ultra-short pulse corresponding to E1 is about 20 ns, and thus a commercial coupling clamp injection device used in typical high-voltage tests may be used. However, when a test is desired to be conducted on a non-nuclear electromagnetic pulse (HPEM), there is required a high-voltage wideband injection device that satisfies a reaction time corresponding to the rising time of several hundreds of ps and frequency performance.
Such high-voltage sub-nanosecond pulse injection devices may be divided into an inductive type and a capacitive type, wherein the capacitive type is more effective as a method of coupling high-frequency pulses having a short rising time.
Prior art related to this includes the paper entitled “Capacitive Coupling Clamp” published in IEEE SoftCOM conference in 2008. FIG. 1 is a diagram showing the core part of the paper, wherein most commercial coupling clamp injection devices that are currently sold have a structure and specification similar to those of the device in the paper. As specified in International Electrotechnical Commission (IEC) 61000-4-4 standard, an electrical fast transient/burst (EFT/B) is implemented to be coupled to a cable. A characteristic impedance is 50Ω, N-type connectors are used for input/output terminals, and a termination resistor of 50Ω is connected to the end of the device.
The coupling clamp injection device presented in the paper is designed to be capable of injecting pulses of up to 5 kV based on a pulse of 8/20 μs (rising time/pulse width), and injecting a pulse of 5/50 ns.
However, since the device is implemented using N-type I/O connectors having an insulation withstanding voltage, it cannot be used at a pulse having a peak voltage of several tens of kV or more. Further, since the device is implemented to be capable of injecting a pulse having a rising time of 5 ns, it may be difficult to use the device due to the problem of a parasitic component and impedance mismatch when a wideband pulse having a rising time of several hundreds of ps or less is injected. Therefore, it is difficult to use the coupling clamp injection device presented in the exiting paper or existing standards as a test device for injecting a high-voltage wideband pulse having a peak voltage of several tens of kV and having a rising time of several hundreds of ps or less.
Another prior art includes U.S. Pat. No. 5,477,153 (entitled “Electromagnetic pulse coupling network”). A coupling network device to be used for an effectiveness analysis test for a high-power electromagnetic pulse, which is disclosed in U.S. Pat. No. 5,477,153, is composed of three dummies (stacks) 1, 2, and 3 made of a circular ferrite core, as shown in FIG. 2. The two stacks 1 and 2 have the same diameter, and the third stack 3 has a diameter identical to the sum of the diameters of the two stacks 1 and 2. The central section of the first two stacks 1 and 2 configures a primary winding using a copper tube 4. A secondary winding is configured such that an insulting wire is wound around the first two stacks 1 and 2 to implement a 1:2 boosting step-up transformer, and the third stack 3 is configured to be coupled to the cable of a Device Under Test (DUT). The device disclosed in U.S. Pat. No. 5,477,153 is designed in an inductive coupling type, wherein a use frequency band ranges to 100 MHz, and a peak voltage of up to 3 kV is usable.
When calculation is made using the following Equation (1), frequencies of up to GHz must be usable so as to inject a pulse having a rising time of several hundreds of ps or less, but the injection device presented in U.S. Pat. No. 5,477,153 is disadvantageous in that only frequencies of up to 100 MHz can be used, and the magnitude of an injectable peak voltage is small, thus making it difficult to use the device as a device for injecting a high-voltage wideband pulse having a peak voltage of several tens of kV or more and having a rising time of several hundreds of ps.
                              f                      3            ⁢                                                  ⁢            d            ⁢                                                  ⁢            B                          ≈                  0.35                      t            r                                              (        1        )            where f3dB denotes a 3 dB bandwidth and tr denotes a rising time.
The above Equation (1) shows the frequency bandwidth depending on the rising time in a pulse waveform.
Although not shown in detail in the drawing, Montena EMC of Switzerland currently sells an injection device for coupling a high altitude electromagnetic pulse (HEMP) to a cable. This scheme has been developed to inject a short pulse in a coupling manner upon performing a pulsed current injection (PCI) test in the standard MIL-STD-188-125. This enables an E1 pulse of HEMP having a rising time of 20 ns to be injected at a maximum of 100 kV. This device has a sufficient injection voltage, but it is impossible to use the device to inject a wideband pulse having a rising time of several hundreds of ps.